Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.76	11.312%	$187.8501	$187.85	$187.85	$187.90
Purchase #2	$238.43	6.381%	$253.6442	$253.64	$253.65	$253.60
Purchase #3	$90.83	8.854%	$98.8721	$98.87	$98.85	$98.90
Purchase #4	$43.71	5.474%	$46.1027	$46.10	$46.10	$46.10
Purchase #5	$31.34	3.291%	$32.3714	$32.37	$32.35	$32.40
Purchase #6	$153.55	12.359%	$172.5272	$172.53	$172.55	$172.50
Purchase #7	$240.48	3.683%	$249.3369	$249.34	$249.35	$249.30
7 purchase totals =	$967.10		$1,040.7046	$1,040.70	$1,040.70	$1,040.70